That is not disturbing, that is the truth. Do you know how much a 1:1 30Mbps DIA connection costs? 2-4Lakhs a month without any IP prefixes except the /30 for BGP!
Customers wants cheap but they want quality too. That is not how it works. Do you know how much international transit costs; what is the cost for maintaining a sea pipe or just a metro backbone itself?
A big pipe used is divided among many customers; easy way to make it cheap for customers. Kind of like our water supply
It's not an India thing; this is how it is everywhere difference is the pipes there are much bigger since base plans usually start over 100Mbps or even 500Mbps in countries like Tokyo and Singapore.
Not every customer is going to keep saturating all the time hence it rarely affects anybody plus residential TCP have a throttle limit of 35Mbit/s per lane.
You want another cold truth? You know why Jio never has speed issues? Because they take the 3300GB limit very seriously and have enforced it correctly everywhere, while for Airtel well... Airtel is airtel....